JPH07199773A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device of which inside can be cooled without especially adversely affecting another controlling circuit, and in which the life of a cooling fan can be prolonged, in the image forming device provided with the cooling fan. CONSTITUTION:As to this image forming device controlling the driving of a photocoupler 11 and a triac 12, heating a heater 2, keeping the temperature of a heat roll 1 as specified, and thermally fixing a toner image to a paper, the driving controlling circuit 9 of the cooling fan 8 is controlled so as to drive the cooling fan 8 to be turned on/off in a so-called sleep mode, so that the life of the cooling fan 8 is prolonged by efficiently using the cooling fan 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a fixing device and a cooling fan for cooling heat generated by the fixing device.

[0002]

2. Description of the Related Art A printer device using an electrophotographic system,
An image forming apparatus such as an electrophotographic copying machine includes a fixing device for thermally fixing a toner image. In the heat fixing process by the fixing device, the toner image is transferred onto the paper by heat and pressure by sandwiching and conveying the paper on which the toner image is transferred between a heat roll and a pressure contact roll whose heating is controlled to about 180 ° C. It is a fixed thing. Therefore, in the image forming apparatus having the above-described configuration, the heat generated by the heat fixing device causes the temperature inside the machine to be high, and therefore the cooling fan is used for the purpose of efficiently dissipating the heat generated by the heat fixing device to the outside of the machine. .

On the other hand, today there is a strong demand for energy saving,
The same applies to the printer device described above. Therefore, heating and controlling the heat fixing device to a high temperature for a long time without performing the fixing process by the above-described heat fixing device wastes electric power, and in the conventional image forming apparatus, the image forming process is performed for a certain period of time. If not, the so-called sleep mode in which the power supply to the heat fixing device is stopped is entered. In addition, various methods have been proposed in the past as to how to control the cooling fan at this time.

For example, (a) in the sleep mode, the power supply to the thermal fixing device is stopped to reduce the power consumption, and the driving of the cooling fan is also stopped in order to further reduce the power consumption.

Further, (b) a system has been proposed in which the power supply to the thermal fixing device is stopped and the driving of the cooling fan is stopped after a predetermined time has elapsed since the sleep mode was entered. Also,
(C) A method has also been proposed in which a temperature sensor for detecting the temperature inside the device is provided inside the device and the cooling fan is stopped when the temperature falls below a certain value. Furthermore, a method has also been proposed in which a control circuit or the like is arranged at a location that is not affected by heat generated by the heat fixing device.

[0006]

However, the conventional image forming apparatus as described above has the following problems. First,
With method (a), since the cooling fan is stopped at the same time as the power supply to the heat fixing device is stopped, the heat fixing device is maintained at a high temperature for a long time, which adversely affects the control circuit and drive mechanism inside the device. Exert.

Further, in the case of the method (b), the fixed time from entering the sleep mode to stopping the driving of the cooling fan is set so that the temperature inside the apparatus becomes low even in the worst case (high temperature). Since it is necessary, this fixed time is usually set to be long, and the cooling fan is used for a longer time than necessary to shorten the life of the cooling fan.

Further, in the method (c), the temperature sensor is expensive, which causes an increase in the cost of the device. Further, in the case of the method of arranging the control circuit and the like in a location that is not affected by heat generation, the space is required and the apparatus becomes large.

In view of the above circumstances, it is an object of the present invention to provide an image forming apparatus capable of cooling the inside of the apparatus and extending the life of a cooling fan without adversely affecting other control circuits. And

[0010]

The structure of the present invention is applied to an image forming apparatus having a temporary pause control mode for reducing or stopping the energization rate of a fixing heater during a non-operating period of the apparatus. And an intermittent drive control means for intermittently controlling the cooling fan after the start of the temporary stop control mode, and the temperature detection means stops detecting a temperature higher than a predetermined temperature,
Stop control means for stopping the cooling fan.

[0011]

The present invention is a cooling fan used in a printer device, an electrophotographic copying machine, or the like which shifts to a sleep mode (temporary pause control mode) by continuing a certain non-operation period. The cooling fan is intermittently driven by intermittent driving control means such as the above, and the cooling fan is efficiently used to extend the life of the cooling fan.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows a part of a control circuit used in the image forming apparatus of this embodiment, and particularly shows a temperature control circuit of a heat fixing device. As for the configuration of the entire image forming apparatus, for example, the configuration of a known image forming apparatus including a photoconductor drum to which an electrophotographic process is applied, a developing device, a transfer device, and the like can be applied. In the figure, the temperature control circuit includes a heater 2 provided inside the heat roll 1, a thermistor 3 provided in contact with the surface of the heat roll 1, an analog-digital converter (hereinafter referred to as an A / D converter) 4, a micro The processor unit (hereinafter referred to as MPU) 5, an energization / stop circuit 6, an AC power supply 7, a cooling fan 8, and a drive control circuit 9 for the cooling fan.

The thermistor 3 as a temperature detecting means is a temperature sensitive element for detecting the surface temperature of the heat roll 1. The resistance value of the thermistor 3 changes to the resistance value corresponding to the detected temperature, and the lines 10a, 10b, A DC circuit is formed with the resistor Rf to divide the power supply voltage by a predetermined ratio. A / D converter 4
Converts the analog value of the divided voltage supplied via the input Io into 8-bit digital data, and outputs D0.
Output from ~ D7 to MPU5. In this embodiment, the set value of the surface temperature of the thermo roll 1 is 180 ° C.,
The digital data (temperature data) at this time is "25" in decimal notation.

The MPU 5 as the intermittent drive control means and the stop control means is a central processing unit for performing overall control of the image forming apparatus in addition to the temperature control of the heater 2, and controls each unit according to a system program stored inside. I do. Further, the MPU 5 inputs from the terminals D0 'to D7'
The bit temperature data is stored in a RAM (not shown). Further, the MPU 5 is provided with terminals PO1 and PO2, and the terminal PO1
Control signal is output from the energization / stop circuit 6 from the terminal PO2
Outputs a control signal to the drive control circuit 9.

The energizing / stopping circuit 6 comprises a photocoupler 11, a triac 12, resistors R1 to R4, and a capacitor C. The control signal output from the terminal PO1 of the MPU 5 is supplied to the light emitting element 11a of the photocoupler 11, and when the control signal is, for example, a low signal, a current is supplied to the light emitting element 11a via the resistor R1 to turn on the light emitting element 11a. Light. When the light emitting element 11a is turned on, the light receiving element 11b detects the light, a current is passed through the light receiving element 11b, a trigger signal is supplied to the gate (G) of the triac 12, and the triac 12 is turned on. At this time, the resistance R1
The R4 and the capacitor C are used for stabilizing the operation of the triac 12. When a control signal (specifically, a high signal) is output from the terminal PO1, the light emitting element 11a is turned off and the triac 12 is turned off. While the triac 12 is on, AC power is supplied from the AC power supply 7 to the heater 2 to heat the heat roll 1.

On the other hand, the drive control circuit 9 of the cooling fan 8 is
It is composed of two transistors 15 and 16 and resistors R5 to R8. A control signal is output to the transistor 15 from the terminal P02 of the MPU 5 via the resistor R7. Specifically, the terminal P02 outputs a high signal to turn on the transistor 15 (however, the terminal P02 outputs an inverted output). Since it is supplied to the transistor 15, the low signal is supplied to the transistor 15.) When the transistor 15 is turned on, a low signal (approximately ground level) is output to the base (B) of the transistor 16 via the resistor R6, and the transistor 16 is turned on. The cooling fan 8 is connected to the collector (C) of the transistor 16 and the power supply (+ 24V) is connected to the emitter (E). Therefore, when the transistor 16 is turned on, power is supplied from the power supply (+ 24V) to the cooling fan 8 to drive the cooling fan 8.

Next, the drive control operation of the cooling fan in the above configuration will be described below. First, when the power is turned on, the MPU 5 performs an initial setting process of the image forming apparatus, a rotation control of a photosensitive drum (not shown), a bias power supply process to a developing device, and the like. Then, the drive control of the cooling fan 8 is executed according to the flowchart shown in FIG.

First, the MPU 5 determines whether or not the sleep mode is set (step (hereinafter referred to as ST)).
1). As described above, the sleep mode is set when the printing operation is not performed for a certain period of time, and is not normally set to the sleep mode immediately after the power is turned on. Therefore,
The first judgment (ST1) is N (no). Therefore, the MPU 5 first receives the transistor 15 from the terminal P02.
Outputs a high signal (control signal) to the transistor 15,
16 are sequentially turned on to drive the cooling fan 8 (ST
2). Next, the temperature of the heat roll 1 is measured by the thermistor 3 described above to determine whether or not the heat roll 1 is at the set temperature (ST.
3). As described above, the temperature of the thermo roll 1 is measured by outputting the output of the thermistor 3 to the A / D converter 4 and inputting and judging the signal converted into 8-bit digital data by the MPU 5. If the MPU 5 determines that the temperature is lower than the preset temperature of the heat roll 1 (ST3 is less than) based on the temperature data, the heater 2 is turned on (ST4). Immediately after the power is turned on, the apparatus itself is at room temperature, and therefore the thermo roll 1 is also at room temperature. Therefore, in the first process, the heater 2 is energized to heat the heat roll 1. Specifically, this process is a control for outputting a low signal (control signal) from the terminal PO1 of the CPU 5 to the photocoupler 11, turning on the triac 12 and supplying electric power to the heater 2.
A period T1 in FIG. 3 shows a temperature change of the thermo roll 1 by the control at this time.

After that, when the temperature of the heat roll 1 rises and reaches the set temperature (ST3 or more), the power supply to the heater 2 is stopped (ST5). This control is performed by the terminal PO1 of MPU5.
By outputting a high signal from the photocoupler 11 to the photocoupler 11, the triac 12 is turned off and the heater 2 is de-energized. During this energization stop period, the heating process of the heater 2 is stopped, the temperature of the heat roll 1 decreases, and the heat roll 1
Is below the set temperature. Note that this period is shown in FIG.
Period T2.

Therefore, after the lapse of the period T2, the MPU is restarted.
A low signal is output from the terminal PO1 of 5 to the photocoupler 11, the heater 2 is energized, and the heating process for the heat roll 1 is restarted. After that, the above process is repeated (ST1 to S
T4 and ST5), the thermo roll 1 is maintained at a predetermined set temperature (for example, 180 ° C).

After that, when the time T elapses from the time when the set temperature is first exceeded (indicated by A in FIG. 3), the MPU 5 shifts to the sleep mode (ST1 is Y (yes)). The determination of the sleep mode is performed by the MPU 5 starting a timer (not shown) from the time point A in FIG. 3 and determining whether the time T has elapsed. This sleep mode is a control performed to prevent power consumption to the heat roll 1 and the like when the printing process is not performed for a certain period (time T in this embodiment) as described above. Therefore, when set to sleep mode, M
PU5 outputs a high signal from the terminal PO1, turns off the triac 12, and stops energizing the heater 2 (ST6,
B) shown in FIG.

Further, at this time, it is judged whether or not the temperature is the stop temperature of the cooling fan 8 (ST7). The stop temperature of the cooling fan 8 is lower than the set temperature (180 ° C.) described above, and is a temperature at which it is not necessary to drive the cooling fan 8 to cool the inside of the apparatus. This first judgment is for the thermo roll 1
Is almost 180 ° C, it is judged (ST7 is N),
While the cooling fan 8 continues to rotate, it is determined whether or not a timer described later is in operation (ST8). Since the timer is not driven at first, the timer is set to the time T3 (however, this timer has the above-mentioned time. A timer that counts T may be used) or a timer is started (ST9 is N, ST1).
0). After that, the above-mentioned timer counting process is continued until this timer times out (ST11 is N).

During this period, the energization of the heater 2 is stopped as described above (ST6), and the temperature of the heat roll 1 gradually decreases. Since the cooling fan 8 continues to be driven by the above-described process, it cools the heat of the temperature of the heat roll 1 (at first, the temperature is close to 180 ° C). After that, when the timer time T3 has elapsed (ST11 is Y), a low signal is output from the terminal P02 of the MPU 5, and the driving of the cooling fan 8 is stopped (ST1).
2). In addition, the time T4 is immediately set in the timer and the timer is started (ST13).

After that, the driving of the cooling fan 8 is stopped, but the temperature of the heat roll 1 continues to decrease during this period (ST8 is stopped, ST14 is N, ST15 is N). Then, when the timer time T4 is reached (ST15 is Y), a high signal is output from the terminal P02 and the driving of the cooling fan 8 is restarted (ST.
16). Hereinafter, the above process is repeated. However, when the driving of the cooling fan 8 is stopped (ST8 is stopped) and the temperature of the thermal roll 1 is increased (ST14 is Y), the counting process of the timer is stopped and the driving of the cooling fan 8 is immediately restarted (ST1).
7, ST16). In this case, the temperature of the heat roll 1 rises for some reason, and if the cooling fan 8 is kept stopped, the temperature inside the device rises and it is dangerous. Therefore, the drive of the cooling fan 8 is restarted. Is.

While the cooling fan 8 is continuously driven and stopped, the temperature of the heat roll 1 is set to the fixing possible temperature (180
When the temperature rises to (° C) (ST18 or above), the cooling fan 8 is immediately driven also at this time to suppress the temperature rise in the apparatus (ST19).

During the on / off processing of the cooling fan 8 described above, the temperature of the heat roll 1 continues to decrease, and when the temperature of the heat roll 1 reaches the stop temperature of the cooling fan or less (Y in ST7), the cooling fan is cooled. 8 is stopped (ST12). In this case, the following timer start processing is not performed.

As shown in FIG. 3, when the temperature of the heat roll 1 reaches room temperature, the sleep mode is released. When the temperature of the heat roll 1 becomes equal to or higher than the stop temperature of the cooling fan 8 and the temperature of the heat roll 1 becomes equal to or higher than the stop temperature of the cooling fan 8 after the ON / OFF drive of the cooling fan 1 is stopped. ,
As shown in the period T3 ′ in FIG. 3, the timer time T3 ′ is set and the cooling fan 8 is driven again.

As described above, according to the present embodiment, in the sleep mode, the cooling fan 8 is controlled to be turned on and off until the temperature becomes equal to or lower than a constant temperature (stop temperature of the cooling fan 8), and the cooling fan 8 is intermittently driven to thereby cool the cooling fan. 8 is used efficiently and the life of the cooling fan 8 is extended.

[0029]

According to the present invention, since the cooling fan is driven intermittently in the sleep mode, the life of the cooling fan can be extended.

Further, in the sleep mode, even if the temperature of the fixing device rises for some reason, there is no danger of immediately restarting the cooling fan and raising the temperature of the device. Furthermore, it is not necessary to dispose a control circuit or the like at a location that is not affected by heat generation, and it is possible to prevent the apparatus from becoming large.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a temperature control circuit used in an image forming apparatus of this embodiment.

FIG. 2 is a flowchart illustrating drive control of a cooling fan of the image forming apparatus according to the present exemplary embodiment.

FIG. 3 is a time chart illustrating drive control of a cooling fan of the image forming apparatus according to the present exemplary embodiment.

[Explanation of symbols]

 1 Heat Roll 2 Heater 3 Thermistor 4 A / D Converter 5 MPU 6 Energization / Stop Circuit 7 AC Power Supply 8 Cooling Fan 9 Drive Control Circuit 11 Photocoupler 11a Light-Emitting Element 11b Light-Receiving Element 12 Triac 15, 16 Transistors R1 to R8 Resistance C Capacitor

Claims (1)

[Claims] 1. An image forming apparatus having a temporary pause control mode for reducing or stopping the energization rate of a fixing heater during a period of non-operation of the apparatus, wherein a temperature detection unit and a cooling fan after starting the temporary pause control mode. An image forming apparatus, comprising: an intermittent drive control unit that controls the intermittent drive of the device; and a stop control unit that stops the cooling fan when the temperature detection unit no longer detects a temperature equal to or higher than a predetermined temperature.